1. Field of the Invention
This invention is directed to improving the properties of coal liquids and, in particular, to rendering coal liquids more soluble in common organic solvents and more compatible with petroleum liquids.
2. Description of the Prior Art
A major use of coal liquids, particularly high boiling coal liquids, could be in a fuel blend consisting of both coal and petroleum liquids. Unfortunately, coal liquids, such as those derived by hydrogenation processes, do not appear to be compatible with petroleum liquids in that addition of small amounts of the former to the latter causes precipitation.
Without subscribing to any particular theory, one likely reason for this is that coal liquids are more polar than petroleum liquids, due to the presence of phenolic and carboxylic functionalities. These polar functionalities cause intermolecular association between adjacent coal liquid molecules and tend to hold the coal liquid molecules together by a network of hydrogen bonds. Petroleum liquids, which lack these polar functional groups, cannot participate in the intermolecular association. As a result, segregation occurs, and the petroleum and coal liquids separate into distinct layers.